The java applet seems to behave just fine (recording and playback work) but when I upload the result, the "Uploading..." message is displayed and it never completes. I waited about 20 minutes. Suggest that you add a progress meter or some way to confirm that the upload is happening. Also suggest you add the capability to save the zip file locally so that the recordings are not lost and can be sent it manually.

I have got
a studio quality USB microphone "Snowball" but when I try
to record my voice using the applet it records silence. I tested the
microphone in Audacity - it works (though I need to adjust the sample
rate) and my java seems to be good: java version "1.6.0_03".

What
might be wrong?

P.S.
I am using Russian version of the aplet
http://www.voxforge.org/ru/read